1. Field of the Invention
The present invention relates generally to oilfield production equipment and, more particularly, to a coiled tubing injector apparatus for inserting and removing coiled tubing from a well.
2. Description of the Prior Related Art
Coiled tubing has seen a marked increase in use through the oil and gas industry since its inception. Coiled tubing operations have grown from the limited applications thought feasible in the early 1950's and are now considered a viable solution in multiple operations, including subsea wells, snubbing, fracturing, and even coiled tubing applications. Coiled tubing operations have grown more popular as a result of their rapid mobilization times and generally smaller footprint with respect to traditional well operations. Furthermore, they require less site crew and personnel, in addition to significant cost savings. As applications for coiled tubing have become more numerous, the strength and size of the coiled tubing has increased in options as well. Coiled tubing was generally less than 1 in. in diameter in the beginning, while it can be found now in sizes up to 4 in. in diameter.
Coiled tubing rigs primarily consist of an injector head for inserting and removing the coiled tubing from the wellhead, a spool reel for storing and transporting the coiled tubing, a power pack to power the injector head, and a control room to operate the machinery. The injector head is responsible for gripping the coiled tubing, usually through a series of grippers powered by a chain design, which provide enough force to move the tubing when necessary, without impeding the structural stability of the tubing. Although the other components are required to functionally operate the system, the injector head is the integral part of a coiled tubing rig.
The injector head comprises components that are subject to considerable wear and therefore require frequent maintenance.
The following patents discuss background art related to the above discussed subject matter:
U.S. Pat. No. 8,191,3520, issued Jun. 5, 2012, to Maschek, Jr. et al. discloses a gripper assembly for use within a coiled tubing injector unit. The gripper assembly comprises a carrier for securing the gripper to the chain drive mechanism of the coiled tubing injector unit and a gripping shoe carried by the carrier. The configuration of the gripper assembly permits removal and replacement of the gripping shoe.
U.S. Pat. No. 6,910,530, issued Jun. 28, 2005, to Austbo et al. discloses a coiled tubing injector apparatus for use in inserting coiled tubing into a well, temporarily suspending the coiled tubing, and removing the coiled tubing from the well is described. The apparatus includes a base with a pair of spaced-apart carriages extending upwardly therefrom. The base is part of a frame positioned above a wellhead. The carriages each have a gripper chain drive system rotatably mounted thereon and movable therewith. An actuation and linkage system allows the carriages to move toward and away from one another in a lateral or transverse direction with respect to the superstructure and the base. Thus, the gripper chain systems comprise gripper chains that can be engaged or disengaged from the coiled tubing extending through the apparatus. A wetting fluid basin is positioned below the gripper chains, and support guides engage the coiled tubing below the gripper chains to prevent buckling of the coiled tubing. The gripper chain drive system includes idler sprockets mounted on an idler sprocket shaft. The position of first and second ends of the idler sprocket shaft are monitored, and may be adjusted to maintain a parallel relationship with a drive sprocket shaft on which are mounted drive sprockets supporting the gripper chain.
U.S. Pat. No. 6,347,664, issued Feb. 19, 2002, to Perio, Jr. discloses a coiled tubing injector head comprised of a plurality of endless chains, each of which are at least three links wide, that are positioned around a plurality of sprockets and/or idler rollers within the injector head. A plurality of gripper assemblies are positioned around the middle links of the endless chains. A bearing skate is positioned within the injector head, the bearing skate being comprised of a plurality of bearings in a staggered configuration, the bearings being adapted for rolling engagement with a portion of the gripper assemblies. An injector head is comprised of a plurality of halves, each of the halves being coupled to a positioning bar, the positioning bar having a plurality of openings formed therein, the openings adapted for use in varying the distance between the first and second halves.
U.S. Pat. No. 6,173,769, issued Jan. 16, 2001, to Goode discloses a gripping element of a coiled tubing injector has a carrier and a removable gripping shoe mounted to the carrier. The removable shoe slides onto slots formed on the carrier and is floated on the carrier by inserting an elastomeric pad sandwiched between the carrier and shoe. A manually depressible spring along ones side of the carrier prevents the shoe from sliding out of the slots during operation of the injector.
U.S. Pat. No. 5,918,671, issued Jul. 6, 1999, to Bridges, et al. discloses an injector for flexible tubing has endless drive conveyors on opposite sides of a pathway for the tubing. The drive conveyors include gripper blocks that work in opposing pairs along the tubing pathway. The pairs of gripper blocks are clamped to the tubing and moved along the tubing pathway to either inject the tubing into a well or withdraw the tubing from a well. The gripper blocks are clamped to the tubing by way of skates, which work in opposing pairs. The skates have rollers, with rollers contacting the gripper blocks. Each roller has two ends, which ends are received by bearings inside of mounts on the respective skate.
The above discussed prior art does not address solutions provided by the present invention, which teaches a system that is useful for increasing reliability and reducing the frequency and time required for repairing and/or maintaining injection heads. Consequently, those skilled in the art will appreciate the present invention that addresses the above described and other problems.